"We have cried, we have gotten depressed, but that doesn't help your children," Glenn O'Neill tells PEOPLE
Credit: O'Neill Family

The number 428 means everything to the O’Neill family.

It’s the number of days that they have been living in self-imposed quarantine – in hopes that it will lower the chances of their daughter Eliza become sicker.

Every morning, they cross off another day on a large piece of paper that hangs in their kitchen.

On Friday, the family spoke to PEOPLE about they will continue living this “unconventional life” because their daughter, along with her big brother, Beckham, 8, mean more than anything to them.

Months of Isolation

Exactly two years ago, Glenn and Cara O’Neill experienced every parent’s worst nightmare: their happy and energetic daughter, Eliza, was diagnosed with a deadly disease.

Eliza suffers from Sanfilippo syndrome–Type A, a rare and ultimately fatal genetic disorder that primarily affects the brain.

The 5-year-old is slowly losing her ability to speak, and by the age of 6, she will most likely not be able to talk at all. By 10, most children with the disease are wheelchair-bound and need round-the-clock care.

But at the O’Neills’ house in Columbia, South Carolina, there is rarely talk about the frightening road ahead. Instead, the family is focused on the here and now – and that includes hope for a cure.

“We have tried the alternative,” Glenn, 42, tells PEOPLE. “At times, we have been negative. We have cried, we have gotten depressed, but that doesn’t help your children or your spouse. We don’t get to crawl into the cave. We make a conscious effort to be positive.”

Contracting and building immunity to one particular virus could lower Eliza’s chances of being approved to be part of a clinical trial that could give her a chance to survive. Through fundraising, in two years the family has raised $2.5 million to help fund the research to stop this disease and hopefully give Eliza that chance.

She could get the virus, which doesn’t show any symptoms, from interacting with friends and going to school.

“Her body would then reject the gene therapy,” Glenn says. “So when the trial happens, she wouldn’t be able to take part in it. We are not going to risk that.”

When Cara, who had to quit her job as a pediatrician to take care of her children, and Glenn were told that researchers at Nationwide Children’s Hospital developed a form of gene therapy that they believe could be a cure for the syndrome, they knew that the steep $2.5 million cost wouldn’t stop them.

“Our lives became all about raising every dollar we could. Money wasn’t going to stop us,” says Glenn, who is able to work remotely from home as a consultant at Symantec. “But now that it’s happened, it’s just a waiting game for it to start.”

As they continue to wait, Glenn and Cara see their daughter showing more and more effects of the disease, which makes even the smallest of triumphs huge wins in their family.

When Eliza strings words together to make a sentence, which doesn’t happen as often now, they write it down.

“Our life is like a roller coaster, but one that is always slanted downward,” Glenn says. “We do have the ups and downs, but every day it’s only getting worse. It sounds crazy to say, but you want your child to talk. Watching her lose her ability to communicate is unimaginable.”

When they do leave their house, they go to places where they won’t have to interact with anyone.

“Eliza can still run around, so we take her to state parks with trails,” Glenn says. “We go to deserted beaches or even just take a simple walk down the block.”

Beckham, who also had to be taken out of school so he wouldn’t bring home germs, is a “trooper” and understands why they’re doing this as a family.

“I don’t want her to have Sanfilippo anymore,” he tells PEOPLE. “It messes up her brain and I want her brain to be normal.”

The family’s groceries are delivered and wiped off before they enter the house. And when someone comes over, which is a rare occurrence, they have to wear gloves and a mask.

On Valentine’s Day this year, Glenn didn’t want Eliza to miss out on her school dance, so he brought the dance to her.

“We got dressed up and had a dance party,” he says.

“We are all in this together,” he adds. “We are hoping we land a miracle.”

A Cure for All

The O’Neills are not just fighting for Eliza’s life – they want to give other kids with Sanfilippo syndrome a chance too.

Families around the country who have children with the disorder have started their own Facebook pages to raise money and awareness for the Cure Sanfilippo Foundation.

They’re currently trying to raise $150,000 towards the foundation’s goal of reaching $2 million on their GoFundMe.

“Time is the most precious commodity with this syndrome, and Eliza doesn’t have any more time before it’s too late,” Glenn says.

On July 17, exactly two years after they were first given the news that changed their lives forever, the young family will go to the same beach they escaped to after Eliza’s diagnosis.

They will swim, and even if just for a moment, they will try to forget that their daughter’s future is so uncertain.

“Every positive message we receive, every dollar that’s donated and every time we see our kids smile, we only become more motivated to keep going,” Glenn says. “We will never give up.”